This invention relates generally to wireless communications and more particularly to antennas used within such wireless communication systems.
As is known, an antenna is an essential element for every wireless communication device regardless of what type of wireless communication system the device is used in. The antenna provides a wireless interface for the wireless communication device, which may be a radio, cellular telephone, pager, station (for wireless local area network, wireless internet, et cetera). The particular type of wireless communication system, which prescribes the transmission frequencies, reception frequencies and power levels, dictates the performance requirements for the antenna.
Since most wireless communication devices are handheld or portable devices, each component comprising these devices must be small, efficient, economical and lightweight. The antenna is no exception; it too must be small, efficient, economical and lightweight. To achieve these requirements, many antenna have been developed having various structures including dipole, patch, inverted F, L, et cetera.
In recent years, fabricating an antenna on a printed circuit board has become popular for low power systems due to its low cost and low profile. Such printed circuit board antennas are shaped as rectangles, circles, triangles, or strips and may be modified with notches or slits. The particular shape of an antenna is typically based on the application. For example, an L shaped strip or meandering strips are typically used for wireless local area network applications.
To provide signals to and/or receive signals from a printed circuit board antenna, a feed is used. Such a feed may be a coaxial cable or printed transmission line feed. In most instances, the feed is considered part of an antenna assembly.
While the various types of antennas and corresponding shapes provide adequate antenna performance, they are not optimized to consume the smallest printed circuit board real estate possible nor are they optimized for maximum bandwidth. Therefore, a need exists for a printed antenna that optimizes both size (i.e., achieves smallest size possible) and bandwidth.
The printed antenna disclosed herein substantially meets these needs and others. The printed antenna includes a 1st dipole section and a 2nd dipole section. The 1st dipole section includes a 1st radiation section and a 1st frequency section. The 2nd dipole antenna section includes a 2nd radiation section and a 2nd frequency section. The 1st and 2nd dipole antenna sections are electrically coupled together such that the currents flowing through the 1st and 2nd frequency sections substantially cancel and the current flowing through the 1st and 2nd radiation sections are substantially cumulative. Such a printed antenna may be printed on an integrated circuit or on a printed circuit board and have a one-half wavelength to radiate and/or receive high frequencies signals.
In one embodiment of a half wavelength printed antenna, the 1st and 2nd dipole antenna sections have a cumulative shape that approximates a sinX/X waveform. With such a geometry, the bandwidth of the antenna is maximized and the required real estate to implement the antenna is minimized.
For full wavelength printed antennas, the 1st dipole antenna section and 2nd dipole antenna section are electrically coupled together. With the electrical coupling, the currents generated by the 1st and 2nd frequency sections of the 1st and 2nd dipole antenna sections are substantially cumulative while the currents flowing through the 1st and 2nd radiation sections of the 1st and 2nd dipole antenna sections substantially cancel. In an embodiment of a full wavelength printed antenna, the cumulative geometry of the 1st and 2nd dipole antenna sections may approximate a sinX/X waveform.
The half wavelength or full wavelength printed antenna may include a ground plane that is fabricated on another layer and is substantially parallel to the printed antenna. In addition, the full wavelength or half wavelength printed antenna may include an input/output connection located at a predetermined position to obtain a desired load impedance. Such an input/output connection may be a coaxial probe, printed micro-strip and/or coplanar transmission line.